We demonstrate the use of dynamic decoupling techniques to extend the coherence time of a single memory qubit by nearly two orders of magnitude. By extending the Hahn spin-echo technique to correct for unknown, arbitrary polynomial variations in the qubit precession frequency, we show analytically that the required sequence of pi-pulses is identical to the Uhrig dynamic decoupling (UDD) sequence. We compare UDD and CPMG sequences applied to a single Ca-43 trapped-ion qubit and find that they afford comparable protection in our ambient noise environment.
@article{arxiv.1009.6189,
title = {Keeping a Single Qubit Alive by Experimental Dynamic Decoupling},
author = {David J. Szwer and Simon C. Webster and Andrew M. Steane and David M. Lucas},
journal= {arXiv preprint arXiv:1009.6189},
year = {2011}
}